背景放线菌是一种丝状、分枝、厌氧革兰氏阳性芽孢杆菌，通常作为口腔中的共生生物发现，可导致不同解剖区域的罕见慢性细菌感染。胸壁受累是一种不常见的表现，给诊断带来了重大挑战。本报告重点关注一名 13 岁男孩的病例，该男孩患有胸壁放线菌瘤，影像学上与尤文肉瘤非常相似。病例报告 我们介绍一名没有病史的 13 岁男性病例，他因运动跌倒后出现进行性左侧胸痛就诊于急诊科。体检发现左前胸壁轻度肿胀和压痛。胸部计算机断层扫描 (CT) 扫描显示，左下胸壁有一个大肿瘤，提示为尤文肉瘤。然而，组织病理学检查意外地证实了胸壁放线菌病。立即开始静脉注射青霉素G 4 周。治疗 4 周后的后续 CT 扫描显示，治疗效果显着，胸壁肿块明显缩小。随后患者继续口服阿莫西林维持治疗 12 个月。在此期间，胸壁肿块完全消退，没有观察到明显的不良事件或并发症。结论 该病例强调了在出现胸壁肿块的患者中考虑胸壁放线菌病等不常见鉴别诊断的重要性。与这种罕见疾病相关的诊断复杂性强调需要综合评估策略，结合组织病理学检查和成像。

BACKGROUND Actinomyces, a filamentous, branching, anaerobic gram-positive bacillus, typically found as a commensal organism in the oral cavity, can lead to rare chronic bacterial infections in various anatomical regions. Chest wall involvement represents an uncommon presentation, posing significant diagnostic challenges. This report focuses on the case of a 13-year-old boy presenting with chest wall actinomycetoma that closely resembled Ewing sarcoma on imaging. CASE REPORT We present the case of a 13-year-old male with no previous medical history who presented to the Emergency Department with progressive left-sided chest pain following a sports-related fall. Physical examination revealed mild swelling and tenderness on the left anterior chest wall. A chest computed tomography (CT) scan revealed a large tumor involving the lower left chest wall, suggesting Ewing sarcoma. However, a histopathological examination unexpectedly confirmed actinomycosis of the chest wall. Intravenous penicillin G was promptly initiated for 4 weeks. A follow-up CT scan after 4 weeks of therapy demonstrated a significant response with notable reduction in the size of the chest wall mass. The patient then continued with maintenance therapy using oral amoxicillin for 12 months. Throughout this period, complete resolution of the chest wall mass occurred, with no significant adverse events or complications observed. CONCLUSIONS This case highlights the importance of considering uncommon differential diagnoses like chest wall actinomycosis in patients presenting with chest wall masses. The diagnostic complexities associated with this rare condition emphasize the need for a comprehensive evaluation strategy, incorporating histopathological examination and imaging.